The present invention relates to an illumination type keyboard used as an input device in an electronic apparatus such as a personal computer or a word processor.
As personal computers and word processors have widely spread throughout the markets, keyboards, as their input devices, are desired to have multiple functions. For example, keyboards are demanded where characters, symbols, or pictures on buttons as well as other controls are illuminated for explicitly identifying the key functions under a dim ambient condition.
A conventional illumination type keyboard will be explained referring to FIG. 6.
FIG. 6 is a cross sectional view of the conventional illumination type keyboard. A push-button 1 made of dark color insulating resin has a display head 1A provided at the top thereof in semi-transparent or milky color and arranged of a character, symbol, or picture shape. A switching contact 2 below the push button 1 includes a circuit board 3, a flexible insulating film 4, and an insulating spacer 5 coated at both sides with an adhesive for bonding the board 3 and the film 4. The circuit board 3 has a fixed contact 3A on the upper side thereof as being spaced by a distance from a movable contact 4A provided on the lower side of the insulating film 4, thus functioning as a membrane switch.
An electro-luminescence (EL) element 6 is provided beneath the push button 1. A substrate 7 of light-transmissible material having a film form has a light-transmissible electrode layer 8 of, e.g., indium tin oxide on the lower side thereof by sputtering or electron beam method. The subsstrate 7 has an aperture 7A provided therein for accepting downwardly-extending pressing portion 1B of the push button 1.
On the upper side of the light-transmissible electrode layer 8, a light-emitting layer 9 made of synthetic resin with light emitting material dispersed therein such as zinc sulfide, a dielectric layer 10 made of synthetic resin with barium titanate dispersed therein, and a back electrode layer 11 made of silver or carbon resin are formed by printing. Those layers are covered with an insulating layer 12 of epoxy resin or polyester resin.
The switching contact 2 and the EL element 6 are protected with a case 13 of insulating resin having an opening provided in the upper side thereof through which the push button 1 extends outwardly for upward and downward movement.
When the push button 1 is pressed down, the pressing portion 1B urges from upper and deflects the insulating film 4 to make a direct contact between the movable contact 4A and the fixed contact 3A on the circuit board 3 for implementing an electrical switching operation.
When the EL element 6 is energized with a voltage between the light-transmissible electrode layer 8 and the back electrode layer 11, the light emitting layer 9 emits light which illuminates the push button 1 from its back. This allows an operator to clearly view the position of the push button 1 and the character of the display head 1A even in a dim condition.
In this manner, the conventional illumination type keyboard allows the push button 1 to be easily identified by the light emitting operation of the EL element 6. However, extra light emitting devices, illumination panels, and other components are necessary in the conventional keyboard when the push button 1 is illuminated individually or in a group to identify their particular functions and operations. This makes the keyboard include a more number of components and will be made complex in its arrangement and make it expensive.
A keyboard includes plural push buttons, plural switching contacts actuated by the push buttons, respectively, for making electrical connection and disconnection, an electronic-luminescence (EL) element provided in a direction to the switching contact about the push buttons, the EL element including separate light-emitting regions for illuminating the push buttons, respectively, and a controller coupled to the EL element and the switching contacts, for controlling an light emitting operation of the EL element to illuminate a certain push button of the push buttons.
The keyboard can thus provide multiple functions for illuminating the push buttons although having a simple structure.